Prime Minister Theresa May was informed about a recent test of the Trident nuclear deterrent when she came into office last year, Downing Street has said.
But the PM's official spokeswoman declined to confirm or deny reports that a missile malfunctioned during the test, stating only that Mrs May was told the operation was completed successfully.
Mrs May refused to answer questions on Sunday over her knowledge of the test, in which an unarmed Trident missile reportedly veered off course off the coast of Florida in June.
But her official spokeswoman has now told reporters that the PM was briefed on the "demonstration and shakedown" operation undertaken by HMS Vengeance on its return to service following a refit.
The PM was informed that the operation was successful, allowing Vengeance and its crew to return to service.
The spokeswoman told a regular Westminster media briefing that, as a matter of long-standing policy, the government did not publicly discuss the operational detail of exercises of this type.
A defence minister is to be forced to come to the House of Commons for a grilling on the incident, after Speaker John Bercow granted an urgent question on Trident from Labour's former defence minister Kevan Jones.
Mrs May has come under pressure to set out what she knew about the operation, after the Sunday Times claimed there had been a cover-up of a failed test of the Trident II D5 missile.
Appearing on BBC1's Andrew Marr Show on Sunday, the Prime Minister ducked four opportunities to disclose whether she was aware of a problem at the time she addressed MPs before a Commons vote last July to approve the £40 billion Trident renewal programme.
Asked on Monday whether Mrs May had in fact been informed of the result of the test prior to the Commons vote, the PM's spokeswoman said:
"The Defence Secretary and the Prime Minister are routinely informed when one of these specific 'demonstration and shakedown' operations are planned and on the outcome of them."
"In this instance, that was in June so it was under the then prime minister (David Cameron). On taking office, the current Prime Minister was briefed on a range of nuclear issues, including this."
The spokeswoman declined to say whether Mrs May was informed of a malfunction in the missile system, stating that it was not Government policy to discuss operational details of tests in public, and telling reporters that she did not anyway "accept the premise of the question". She added:
"We have been clear that the submarine and the crew were successfully tested and certified. That was the purpose of the operation."
"What is also clear is that the capability and effectiveness of the Trident missile is unquestionable."